Mechanical design engineer here. I work in the steel industry. We have a little saying: “don’t make bathtubs” - means never weld something that could potentially pool water without putting in a drainage hole. Your engine mounts look nice and sturdy to me, but I’d put a little drainage hole in the bottom there.

Hey!! Thanks for the shout out guys! I’m here if you ever need some help with the project.

Don’t forget to put something like Tef Gel or Anti Seize on the bolts used to mount your outboards. Aluminum and steel will create galvanic corrosion.

Chris I think this build is awesome but I would recommend a bow thruster. It going to make moving that beast in tight areas.

Don't forget drain hole on bottom of engine mount

Just a thought Chris, you should consider mounting a bilge pump inside the hot tub compartment before you mount the hot tub shell. I think your future self will thank you for providing a way to vacate the water that may or may not get in there.

Hi Chris, I think that a Transom Plate across the entire rear would be the way to go, since this will transfer the pushing force of the engine to the boat more evenly. Single transom plates will cause more stress on your structure ...

Hey Legends, I'm was a Marine Engineer in the Australian Army, I worked quite a lot on out open water dual hull SharkCat. It had twin Mercury Verados as well. I would investigate the FSU (Fuel Supply Units) on both engines before you launch into the water. This job is not too hard to swap the FSU out, but you need to be on dry dock.

Im a marine outboard technician. I wouldnt have gone with used mercs but thats more of a personal preference. Make sure all the services are done. Id go down the service chart and do each and every thing regardless of the previous owner or seller said they were done. Id also get in contact with a merc dealer and make sure all the recall work was done. Also idk what the salt content is in the water over there, but id also replace every anode.

Make sure your hot tub has its own bilge under it. Nothing like getting a leak you dont know about to ruin your trip or your boat.

As a marine technician, all I can say is good luck with two 1200 hour verados. Not the move I would have made, but, it'll make for good content 😂

You could add a "skid plate" along the whole bottom, joining the 2 inner pontoons from the hottub enclosure all the way to the transom at the back, and it would add a lot of buoyancy, stability and storage, and it would be a big flat trimaran and give you a better flow of water over the propellers.

I still think you should finish weld the bottom strakes that don't connect between the pontoons. Buy two engines setback brackets and tie both engine mounts to each other as a solid Transom. You need a good two to three inch thick transom that ties to all four of the pontoons.

It's like the flybridge off a yacht, on a dock, with motors. Admittedly, the flybridge is always the best place to be.

You should look into maybe getting a manual or a hydraulic jackplate for your outboards. If you want the pontoonboat to go faster, that might be needed.

200kW per engine is a lot of power. Don’t want to sound pessimistic, but in my case 150hp (100kW) engine ripped out a similar welded-in engine mount from my “conventional” alu-boat after a few years. I’d really consider additional struts and braces to ensure the lower weld seam does not crack the pontoon. Thinking out loud.

You can buy the steering system from seastar to have them go whatever direction you want independently fyi.

This stage would be an excellent opportunity to create some plates that lock all four pontoons together then. Mount the engines 😊

Im a marine engineer from Indonesia… here we say ‘it it stays afloat, you have built a boat’

Your lower cavitation plate should be 1/2 to 1 inch above the bottom of the pontoon. Make sure the TOP of your motor mount is very strong.

This is sosooo badass, i find myself waiting patiently for the new vid drop with construction on this beast

I’m looking forward to seeing this thing motoring through the water. I honestly think it’s going to be really cool for what you want it to do. Good luck. You have a knack for making crazy stuff work, and I support the chaos. I still have the sticker to prove it.

Always a pleasure to be here and glad to see you hot glueing more Aluminum and horsepower to (our) party boat.

40ft long, 500hp with 1000+ lbs of water in the bow. What could go wrong.

I’m loving this build and can’t wait to see it on water no matter what the results may be.

Either put those engines on with the best bolts or get the best quality GPS to mark the spot when you lose one or both.

This makes me want to build my own pontoon! I think Jiggin with Jordan has a pretty cool pontoon/houseboat. would be so cool to see a hybrid of your idea and his.

Cool project, excited to follow this build! Never thought I’d be excited to follow a boat build! 😂😊

500hp is chicken feed for that size lol. We have 4 - 500r's on 36' cats. Damn, we even have 2 - 500r's on tri-toons. 500hp is nothing for that massive toon haha

Hey Chris, the yacht is considered 'inboard' motors as they are inside of the hull. These are certainly not inboard in the slightest... but they are central outboard I believe

Thank you for all the hard work in making these excellent videos.

Ton of work in this video. You guys are amazing!

I was on a catamaran recently and noticed it had an analog depth gauge. Well, digital read out, but analog depth sonar that could read through fiberglass. Pretty accurate as we hit a sandbar from being distracted. Worth considering these quality of life gadgets.

Need longer videos haha. Just found your channel randomly lol. But I definitely dig it. Gnarly fuxkin boat bro. Keep it going. Did I mention I'd love longer hahaha.

Chris insulating the hot tub is a must believe me 😮😮😮... been there done that.. so do that and the cabin don't spare monet on the insulating!!,,,,,,😊😊😊😊

Can't wait to see the trailer you build to haul this monster. Going to need an oversize permit to transport also.

I love how goof this project feels. Can't wait to see how it goes.

I have to say the pressure gauge on each cell is the ULTIMATE fail safe alarm for we’re talking on water!

Loving these boat episodes! Thank you!

I’ve been watching you since your backyard videos. During the Datsun build I had serious doubts and concerns if you would finish that build. I’ve since learned that you get it done even when the chips are down. The boat looks very interesting. Much good luck going forward

I watch your channel before bed because it helps me fall asleep, thank you! I’m your biggest fan!!

Oscar needs a welding table for sure you should make that happen.Specially now and for future builds.

Those twin 250's look nasty....great job guys!

Looking at that hot-tub I'm thinking it might do well with some insulation to not discharge any "hot" out in all directions when it is on water...

Looking good I knew you had a plan the whole time!!!!

Can’t wait to see this went this done 🙌🙌💯💯

literally every fiber of my being cant wait to this to be built so very exciting

Please for the love of gawd do the loaded weight calcifications. This would never get registered in Florida.

This is quite interesting and enjoyable❤.

Love the build, pontoon is massive. Should call it Toontanic

I dont usually like watching long videos, but in this one I am weirdly interested.

didnt know 95% of subscribers here are engineers and boat builders

I suggest you mount the engines on a vertical lift system where you can adjust the depth of your prop depth. I’ve seen these systems on boats in the puget sound for low tide access to shallow areas. It eliminates the tiliting for transport too, you just raise it higher. Also, do NOT enclose your engines! You will trap your exhaust fumes which can starve your engines and possibly go BOOM!

Loving this series

You can use what is called jack plates if your concerned about the height/depth of the props. It gives you a lot of adjustments for outboard engine height and some are motorized to make quick easy adjustments. I don’t know much about boats but I’ve seen them in action on some of my family members boats they are pretty cool.

As a precision welder for over 20 years, for that size of engines overkill on the mounts are always a good idea. The motors are only overkill if your a slow driver. I personally think 1 250 is enough. But I like to just cruise on the lake.

Wow. Looking awesome

I think you are making history on this build and will get many orders.

Good job guys!

Magical build!

Make sure you remember to incorporate zinc anodes to the pontoons if this thing is gonna be in even remotely salty water.

Saalute. Im late. Nice build. Roll cage, sea foam in the pontoons! Expansion foam I think it’s called. . Just spitballing, two tier cruiser. High5s

love this build

The outboard with the steering cylinder mounted to it needs to be mounted to the starboard side. If you’ve truly got a pair of outboards, one is standard rotation, and the other (the one without the sea star cylinder) should be a counter rotating engine. Use the model numbers to verify.

Chris, you must add a drainage hole. Rule of thumb, water will always find a way in, so give it a way to get out. Trust me. I'm not an engineer and I have zero experience in buildings boats. I'm just reiterating what I've read in the comment section 🤓

Looks ready to take for a cruise to me!

Hey chris, for a boat of this size i would've thought you needed at least 1000HP.

You guys rock. Enough said.

Oscar. Damn that boy can weld. 👍😁 Pure talent. 🙏

i'm curious if the hot tub will make this thing a total sea plow once it gets in the water.

Hey I commented about air pressure and gauges to check for leaks haha. I don’t know if you saw mine or someone else’s but that’s awesome regardless!

Consider putting ski runners under the outside pontoons to turn this into a pontoon hydrofoil to reduce drag on plane. Have the engine mounts able to drop down when on plane on skis, the power trim that also allows vertical movement so you can adjust engine out drive height on the fly which addresses shallow water performance. Please consider the name this the Disco Volante II

I love this project. Have you considered some sort of bow thruster? That’s a lot of boat.

That transom mount on those engines is cast and machined where I work! If you look inside the webbing on the boat side of it, you'll see LSI (LeSueur Inc) cast into it.

I wouldn't forget to put a aluminum band welded over the butt joints on the pontoons. That is a major weak point could see cracking/splitting issues once it hits water with all the weight all over the boat.

Excellent build

Be sure to have two 55 gallon drums filled with water. Make sure that the prop and about one foot of the engine is pointed down into them. You can burn these engines quick if you dry ran i t...if you haven't thought of a bathroom. On that I'd do it especially just right into the water.

A small addition that would increase the strength of the engine mounts would be to extend the lower corners of the mounting out to the edge of the pontoon cylinder cap. This will take bending loads out of the cap sheet material and add to overall strength of the mount overall.

Hello!! I was watching the series on the pontoon hatch, awesome. I would like to suggest one thing though, keeping in mind the purpose of this (party, people) I loved the length of it, but it didn’t sit right with me that it was super long, but were kind of limited on width. I understand the limitation ( parking spot!) , but was thinking that you could extend the width if you add 90 degree folding floor on the left and right. So when parking you could have them verticle, (saving space, fitting in the parking spot) and while your out and about, you can lower them extending the floor space!!! Doesn’t need to be that much, maybe just a small 2-3 fit walk space outside the furniture??? Just a thought!! Have fun!!

Everyone in the comments: "It needs a bow thruster!" Chris: "Harbor freight is sponsoring this build and was nice enough to give us two trolling motors!"

Two minute ago, im fast today. Been here since m240z 3d modeling 😊

Good choice on ob choice - cheap and plentiful parts… still lots of new-in-crate floating around… might I suggest jackplates… far easier to adjust on the fly when the time comes… and that time will…. ( 3 cats and 8 jackplates myself )

I feel like this things is going to be hard to turn with these outboards, being mounted "inboard"

My thoughts exactly. "Better to be overkill than underkill."

As an okie from Oklahoma I would suggest you just build you. Sounds like you got it figured out. I just subscribed.

Yo Dawg Oscar does all the work and then you we got this done !!

I was really hoping it would have some seven marine 557hp LS powered outboards

The Pontyacht..? Yachtoon..? is gonna be sick!

So rad 🤙🤙

I might have run the sides of the engine mounts down further to tie into the plates welded underneath the big tubes, but otherwise looks great.

Awesome boat guys! I think you’ll want more power. I’ve seen smaller boats with twice the power.

Great Series! I have had ideas for the perfect Party Barge and this is really scratching that itch

Remember this ? Welcome to B is for Build. A place where Chris and his friends document their life with cars......

Another thing to look into with the engines depending on where the water pickups sit you might want to get the nose cone water pickups just to be safe

Love this series. You guys are killing it.

You have been watching too much of the guy that built a catamaran ship from his back yard back in the early 90s. His boat called kaliedescope, amazing. Good luck with your build.

Thats a lot of power to put on the end of a pencil , hehehe Difficult to tell from the vid, looks like the motors may be too high. There are adjustable jack plates for rising and lowering the motors

B is for Balls. lets get it ooooon.

Here for all the expert boat builders in the comments 😂

I saw a 24' pontoon on my lake last week with twin 300's